Efficient Electroreduction of CO2 to CO on Porous ZnO Nanosheets with Hydroxyl Groups in Ionic Liquid‐based Electrolytes

Electrochemical reduction of CO2 is a very promising route to realize carbon cycle and alleviate energy shortage. Herein, the porous zinc oxide nanosheets with hydroxyl groups on carbon paper substrates (ZnO(OH)/CP-x,xrepresents the deposition time) were proved to be excellent catalysts for CO2 electroreduction to CO. As far as we know, the hydroxyl groups were first introduced into ZnO catalysts for this reaction, which can enhance the surface areas and improve the capacity of binding CO2 by the formation of hydrogen bond. Especially, the total current density could reach 44.3 mA cm(-2) with 97.8 % Faradaic efficiency (FE) of CO over ZnO(OH)/CP-600 catalysts with moderate hydroxyl groups in 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6, 30 wt%)/acetonitrile/H2O (5 wt%) ternary electrolytes at -2.0 V versus Ag/Ag+, although the self-reduction of the catalysts could be occurred simultaneously during electrolysis. Besides, the composition of the electrolytes also can significantly modulate the catalytic activity and selectivity of CO. The outstanding performance of ZnO(OH)/CP-600 catalyst resulted mainly from the introduction of hydroxyl groups, high surface area, good contact with the substrate, and synergy effect between the catalyst and the electrolyte.